public List getAllProduct(); //正确。定义返回类型
public ArrayList getAllProduct(); //错误！！定义返回类型

public List queryByCritical(Map criticals); //定义参数类型
public List queryByCritical(HashMap criticals); //错误！！定义参数类型

List result = null;//定义类型的时候未List
result = new ArrayList();//只有构造时出现的实现类

Map result = null;//定义类型的时候未Map
result = new HashMap();//只有构造时出现的实现类

String user_name= null;//错误！！！ 即使数据库中这种风格
String userName = null;//正确写法
int CET_SIX=6;//常量命名时用下划线区分单词,字符全部大写

//错误！！不能出现如此写法，需要定义为常量
if(user.getNumber() == 1001 ) {
//do something
}
//正确写法
static final int ADMINISTRATOR_ROLE_NUMBER = 1001;
static final int MIN_WIDTH = 4;
static final int MAX_WIDTH = 999;
static final int GET_THE_CPU = 1

if(user.getNumber() == ADMINISTRATOR_ROLE_NUMBER ) {
//do something
}

//sample code snippet
for(int i=0;i<10;i++){
    ValueObject vo = new ValueObject();
}

//recommend this style
ValueObject vo = null;
for(int i=0;i<10;i++){
   vo = new ValueObject();
}

//sample code snippet
String sql =”INSERT INTO test (”;

Sql+=”column1,column2,values(”
Sql+=”1,2)”

StringBuffer sql = new StringBuffer();
sql.append(”INSERT INTO test (”);
sql.appdend(”column1,column2,values(”);
sql.append(”1,2)”);

if ( condition) //single statement, code here

while ( condition ) //single statement, code here

//IF
if ( condition) {
  //code here
}

//WHILE
while ( condition ) {
  // code here
}

if ( foo ) {
    // code here
}

try {
    // code here
} catch (Exception bar) {
    // code here
} finally {
    // code here
}

while ( true ) {
    // code here
}

System.out.println(" debug 信息");

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

private static Log logger = LogFactory.getLog(SQLTable.class);

logger.debug("debug 信息"); //注意这里没有涉及字符串操作

//涉及字符串操作或者方法调用的，需要用logger.isDebugEnable()来做判断
if(logger.isDebugEnable()){
   logger.debug(String1  + string 2 + string3 + object.callMethod()); 
}

logger.info(""Can't find column to build index. ColName=" + columnName");

try{
   //handle something
} catch (Exception ex) {
   //do nothing. 请确定该exception是否可以被忽略！！！！
}

try{
   //handle something
} catch (Exception ex) {
  ex.printStackTrace ();//不在程序中出现如此写法！！
}

try{
   //handle something
} catch (Exception ex) {
  log.error(ex);//这样将仅仅是输出ex.getMessage(),不能输出stacktrace
}

try{
   //handle something
} catch (Exception ex) {
   log.error("错误描述",ex);//使用log4j做异常记录
}

//sample code snippet
Connection con = null;
Statement st = null;
ResultSet rs = null;

try {
  con = JNDIUtils.getConnection();
  st = …
  rs = …
} finally {
        JDBCUtil.safeClose(rs);//close resultset ,it is optional
        JDBCUtil.safeClose(st);//close statement after close resultset, it is optional
        JDBCUtil.safeClose(con);//make sure release it right now
}

//sample code snippet
String username = …
…
if(“mark”.equals(userName)){
	…
}

//recommend coding convention
import java.util.HashMap;
import java.util.Map;
import java.util.List;

//import java.util.*; NOT!!
//We can use eclipse,right click, choose Source -> Organize Imports
//hotkey：Ctrl+Shift+O

/**
 * $Id: $
 *          
 */

<?xml version="1.0" encoding="UTF-8"?>
<!--
$Id:$ 
-->

//sample code snippet
//TODO issue: the data format, should be fixed

//user table中的该字段允许为null，使用时就需要去check，否则可能出现nullpoint exception
if(user.getDescription()!=null) {
  //do something
}

<input type="text" maxlength = "10" size="20"/>